#include<iostream>

struct TreeNode {
     int val;
     struct TreeNode *left;
     struct TreeNode *right;
 };


bool isUnivalTree(struct TreeNode* root){
    if(root==NULL)return true;
    if(root->left&&root->left->val!=root->val)return false;
    if(root->right&&root->right->val!=root->val)return false;

    return isUnivalTree(root->left)&&isUnivalTree(root->right);
}